1. Field of the Invention
The present invention relates to a work method for stabilizing and greening a slopeside of mudstone or laccolith, especially to a novel work method for producing herbaceous and woody plants on the mudstone or laccolith in order to enhance the application and protection of the mudstone or laccolith.
2. Description of the Prior Art
Generally, all over the world a work method for stabilizing, greening and protecting a sideslope directed to such ordinary sideslopes as sand or stone is well investigated and developed, however, there is not yet efficient stabilization and soil conservation work of mudstone or laccolith, which are notoriously known as ill terrains.
With respect to the characteristics of mudstone or laccolith, generally speaking, it may be classified as follows:
1. A huge and thick rock layer contains no sandstone, except of minority of mudstone, and is young in the geologic time (belongs to the tertiary of the Cenozoic Era). The component granules are minute (smaller than 0.06 mm), low in the content of bound particles, but high in the content of powdery particles, loose in cementary binding, but hard while dry (24 to 37 mm). Due to the high mud content it is low in lithification. Therefore, the exposed weathering face contacted with the atmosphere is extremely apt to generate mud crack during the dehydration and drying, and the width or depth of the crack ranges from 1-2 mm to several cms densely distributed all over the surface of the earth. Just next to it there is a base composed of water impermeable fresh mudstone, and the interface therebetween will form a weathered and peeled-off layer on long term of drought, but when raining the whole piece will slip off and form a damaged face. Thus, the geologic mudstone has no water reserving layer and no subterranean water for use, therefore, water required by the planted plants all relies on extremely few water stored in the rock crack following raining and artificial watering. Because of the difficulty of obtaining water by plants, the survival rate of plants introduced tends to depress fast during drought seasons, especially woody plants.
2. The mudstone or laccolith per se lacks of sufficient cementing force, and has a large disintegration rate, a weak corrosion resistance and a low effective porosity (about 9-14%), so it has a considerably poor water permeability (1.785.times.10-8 cm/sec). In view of this, while raining, the rain can not drain downwardly and tends to produce radial flow on the surface of the earth. Furthermore, the mudstone will be swollen and disintegrated by water, and the existence of superficial crack even accelerates and deepens the depth and rate of water entering into the mudstone resulting in an enlarged scale of collapse and loss. The thickness of superficial soil flushed and eroded annually is about above 10 cm in average. So the mudstone contains few organics and effective nutrients, besides, it contains a large amount of alkaline cations and has a pH between 8 and 9 such that it quite unsuits for the growth of plants.
3. Upon contact with water, the superficial layer will absorb water and swell immediately. Due to a too big difference exists between the internal and external swellings, a shear damage results. The vertical drainage rate of the mudstone is lower than the horizontal one (the ratio therebetween is about 2-5:1). While the superficial layer has a quick dewatering tendency, on the contrary, the internal layer has a slower drainage rate and results in a phenomenum of loose inside and tense outside to peel like an onion and form a huge amount of cracks.
4. In many geographical areas, the dry and wet seasons are quite distinctive therebetween. In the case of Taiwan territory, the rainy season is May to September and the drought on November to April; annual rainfall of 1800 to 2500 mm and maximum single daily rainfall of 350 mm; in April it becomes a high temperature of 25.degree. C. and continues till November. So Taiwan has a weather type of temperature high, drought season long and heavy shower. We can see from the aforementioned characteristics that factors for forming a mudstone, an ill terrain disaster are deadly related to its geographical and climate features and conditions. There are so many relevant factors and complex measurements. Therefore, the methods applied and material employed must be of diversification as well as so many methods are used in combination and the problem can not be overcome only by the usual conventional engineering methods.
Conventional engineering methods while applying to such ill lands like mudstone or laccolith will exhibit the following drawbacks:
1. Radial flow phenomum is easy occured on the mudstone or laccolith while raining and flushes off such material as organic fertilizers, seeds and the like added to the solpeside during the planting engineering. Nutrients required by the plants are unable to be reserved and conserved. Plants are always under conditions of water and nutrients insufficient and infertile resulting in weak plants such that they have lower drought tolerance and an accelerated aging and death. The survival rate of plants planted decreases significantly year after year, especially the woody plants.
2. For ameliorate the abovesaid disadvantages, some engineering works, such as cavity planting, steel pile driving and steel network bed, etc. are tried and attempted to efficiently reserve the nutrition material, but found that the mudstone or laccolith has not only high hardness but also toughness to make manual cavity diging, steel pile driving or even powered drilling hard to be accomplished. Besides, the mudstone has a taboo of no disturbance due to places having been dug or driven become the cause of collapse and slip away while raining.
3. It is long preferrably planting herbaceous plants on the slopeside of mudstone or laccolith because of the advantages, such as fast and quick covering. However, according to the research conducted by Dr. Yamatera, Japan, the pull strength of the root system of herbaceous plants becomes weakened year after year, on the contrary, that of woody plants strenthen year after year because of the root system being penetrated deeply and widely. In this manner, for a long term and effective planting measurement, a concept of complex layered cover plants is introduced, which essentially resides in the choice of plant species. Local perennial dominant landcoverings, grasses and flowers, bushes and tall trees, etc are introduced which may dramatically shorten the time period of natural evolution and substitution, make plants covering on the slopeside of mudstone become a rich and lively scene, and also by utilizing network function of exuberant and dense side root system of grasses and the pile and pole function of a deep root system of a woody plant, both exert grabbing and wraping functions onto the soil to enhance the stabilization and immobilization effects onto the slopeside of mudstone. So, a complex layered covering engineering work is essential for mudstone.
Owing to the upper limit of hardness which may be penetrated by root systems is 25 mm, it is noted in many investigations involving the growth of root system in the mudstone terrain that root systems of both woody and herbaceous plants grow along the crack of mudstone and twist and entangle in the interface between the weathering strata and the original slopeside (of a hardness about 37 mm) but can not go on grow downwardly. Then, after a long time, roots of woody plants grow and enlarge to broaden the gap of the original interface and add onto cracks of weathered strata and the width and depth thereof. Therefore, on raining the work becomes a damaging face and a design good originally has a potential risk of slipage in whole on raining.
4. Conventional planting works and materials are limited by the capabilities and mechanisms, in Taiwan, the typhoon period of July to September and the drought period of October to March of the next year should be evaded. Working period is confined to April to June and becomes a difficult problem to the particular timing of the soil conservation of mudstone.
5. If seeds of both herbaceous and woody plants are planted at the same time on the slopeside, it is easy to handle and saves the cost of complex layered covering works. However, owing to most woody plants are slow in budding and weak than herbaceous plants in early age, the dominant herbaceous plants seriously disturb, even totally block the living space for woody plants. Therefore, for so many years, there is no good results from complex layered covering being conducted by means of seeds.
In view of hands of conventional works being tied up by drawbacks of ill lands, mudstone or laccolith, which are the problems desperately await to be solved in many countries, the present inventors devoted to intensive research and investigation and based on the experience of several decades and field tests as well as amelioration, the present invention is completed.